Oh, I contain it to be unleashed on some poor sap who cuts me off while I'm driving. For some reason, driving just turns on the pent up rage spigot within me and I go into neverending tirades of profanity. In the end, I feel much better and no one has seen my ridiculous meltdown who's opinion I actually care about.
At work, it's a bit more difficult since most of my frustration comes from my coworkers and it's a bit harder to ***** or rage about them without there being repercussions. So yes, it stays deep and pent up inside until something triggers it, usually some minor annoyance that really really doesn't need to be there, like someone not running the cardboard baler when they filled it up. If I'm alone, I'll say out loud something along the lines of, "Fucking idiots, it takes 3 seconds, close the gate and hit the button, it's not hard." If I'm not alone, I'll mutter it under my breath.